Method of preparing oil wells for production



lll E-EEmW` EE W. T. WELLS Filed July 23, 1934 METHODv OF PREPARING OIL WELLS FOR PRODUCTION March 10, 1936.

UNITED STATES PATENT OFFICE METHOD OF PREPARING OIL WELLS FOB. PRODUCTION Walter T. Wells, Glendale, Calif., assigner to The Technicraft Engineering Corporation, Los Angeles, Calif., a corporation of California Application July 23, 1934, Serial No. '136,533

14 Claims. (Cl. 166-21) which materially reduces the number of casing pended from a conducting and supporting cable 3 10 strings needed in order to isolate undesirable forand carrying a plurality of gun units 4 arranged mations from producing formations, thereby efto discharge bullets 5 laterally through the casfecting a substantial saving in both labor and ma ing I. terials; The casing is perforated in two zones desig- Third, to provide a method of this character nated 6 and 1, which. are preferably located 15 whereby the size of the casing, particularly in opposite unproductive formations above and deep-wells may be materially increased; below the several water bearing and oil or gas Fourth, to provide a method of this character bearing formations. The distance between zones which not only materially insures against chan- 8 and 1 is determined by the pressure required to neling of the cement or other diii'icultles that may force water and cement from zone 1 to zone E. 20 occur while cementing in; but is so performed- A'Ihe lower the pressure used, the closer should be that in the event of an imperfect cement job, the the zones. The distance between zones 6 and 1 process maybe repeated withoutl difficulty until is also dependent upon the tightness or concenthe cementing is accomplished to perfection; tricity of the casing in the well bore; that is, the

Fifth, to provide a method of this character area or condition of the passage 8 between the 25 which enables long sections of casing or the entire casing and well bore. In other words, the zones casing to be cemented in; 6 and 1 should be sufliciently close to permit ciru Sixth, to provide a method of this character culation through passage 8 and far enough apart whereby the effectiveness of the cementing job is to embrace as much ofthe oil bearing andwater apparent in the form of accumulations of cement bearing formations as possible. 30 on the apparatus used; and, 1 Upon accomplishing the perforation of zones e Seventh, to provide on the whole a novel methand 1 the gun is withdrawn and a tubing string od of cementing in well casing which is particu- I inserted. Said tubing string is provided with larly flexible in its execution to meet the various a packer I0 of any suitable construction and so conditions and situations encountered in oil well disposed as to occupy a position immediately be- 35 drilling; low zone l. 'I'he tubing string continues below With the above and other objects in View as the packer Il and terminates approximately opmay hereinafter appear, reference is made to the posite the lower none 1. At this end the tubing accompanying drawing in which; string is closed by a plug I I but is provided with 40 Figure 1 is a diagrammatical sectional view of apertures 9a immediately above the plug. 40 a well bore at its lower portion showing a casing It should be noted here, that if the casing is in position after it has been perforated at spaced to be cemented from its extreme lower end, the points, a tubing string run in, and water circulower set or zone of perforations 1 may be omitted lated; Figure 2 is a similar diagrammatical view and the -usual openings provided in the oat or showing the succeeding step in which cement is slice. not shown, but often usedl at the lower en ds 45 circulated through the two sets of perfcrations; of casing in deep wells, may be used. However, and Figure 3 is a similar View showing the final 'www u uch as it is preferable to rest the c on step of perforating the ng and cement oppothe bottom of the bore, it is often better practice site the producing zones. to perforate the lower zone '1 to insure proper l In conjunction with my method of preparing communication with the passagelt.A 5@

an oil well for production, it is intended to drill After the tubing string 9 has been positioned, throughl the several formations whether non-pro` water, indicated by I2, is circulated down through ductive or productive of water, gas or oil. After the tubing string l out the apertures 9a through the desired depth is reached a casing I is lowered. the perforations of zone 1 upward through pas- 'niereaften the casing is perforated by gun- 55.

My invention relates to methods of preparing oil wells for production and the objects of my invention are:

First, to provide a method of this character whereby contamination of oil or gasproducing formation by water introduced in any manner between the casing and well bore is effectively eliminated Second, to provide a method of this character nre. This being accomplished preferably by a perforator gun such as illustrated and described in the following co-pending applications of one, Wilfred G. Lane; Well casing perforator; Serial No. 642,410; filed Nov. 12, 1932; and Method and means for controlling deep well gun-nre for perforating casing; Serial No. 648,049, led December 20, 1932. Said gun is represented diagrammatically in Figure 3 and comprises a body 2 sussage 8 and returning' to the casing i thrcughzone l,soastothoroughlycleanpassagetofdrilling mud and other soluble or loose material.

This washing operation is of substantial importance for it washes accumulations of drilling mud from the walls of the bore so that the cement is applied directly to the formation. Heretofore, in other methods of cementing known to applicant, thismudhasnotbeenremoved exceptin arestricted area adjacent to the bottom of the casing. inasmuch as the mud is more or less soluble in water, its presence between the cement and formation prevents an adequate seal or permanent bond, thereby preventing the cementing in of long sections of the casing. Of course.l it is customary towashtheboretoalimitedextentbeforerunning the casing; but without the circulation established, as explained above. the encrustations of mud are not sumciently removed to-insure a proper bond between the cement and formation.

After inspection of the quantity and. condition ofthewaterreturnlngthroughcasing l hasindicated that a good circulationthrcugn passage l hss been established and the accumulations of deleterious matter removed therefrom, cement It is pumped down the tubing string l and caused to follow the path taken by the water until some of the cement has returned through zone l, as shown in Figure 2. The flow of the cement may be facilitated by inserting a plug il on top of the cement introduced into the tubing string l and then pumping water against the plug to drive it to the-bottom. By making the plug Il of such length as to cover the apertures a it is possible to tell by the pump pressure when the plug has reached the bottom and the cement driven out and into passage l.

It should be noted that water entirely nlls the casing below the packer Il so that the cement can rise no higher therein than rione 1. However, a second packer I l may be disposed immediately above the apertures in the tubing string.

It is preferable to locate the perforations of lone l as close as possible in order to restrict the extent of zone I. This reduces the amount of cement that must return to the casing I in order to close the zone l when the tubing string is withdrawn. Withdrawal is made after the cement has set sumciently to maintain its position but before it is hard. As the tubing string is withdrawn, the packer Il swabs the excs cement out and tends to further close any perforations in sone t.

Ifitisdesiredtocement thecasingfora greater distance than is feasible in a single operation, additional sets of perforations may be made in the adjacent portion of the casing and Vthe washing and cementing operations repeated. This may be continued if desired until the entire casing is completely cemented in. In the repetitions of the process the zone l of the upper section preferably overlaps slightly the zone t of the lower section thereby insuring against any gaps in the cement.

Should a greater distance be provided between zones 8 and I than is practical, or should insumcient cement be introduced, it is merely necessary to perforate again at the calculated upper terminus of the cement and repeat the process.

After the casing has been properly cemented in, the perforator is again lowered and the casing perforated opposite the oil or gas producing formations as shown in Fig. 3. inasmuch as the different formations have been adequately sealed one from the other, the casing may be perforated at any desired point, and it is possible to produce from more than one formation at a time by utilisaosases ing packers between the producing zones and separate means of communication with the surface.

such as a tubing string for one formation and the space between the casing and tubing string for another formation.

I claim:

l. A method of preparing wells for production characterized by; drilling a well bore past a plurality of formations' including non-productive formations and those productive of water. gas, or oil, as the case may be; running a casing in said bore: then providing at least two zones of communication between the casing and the well bore so positioned to embrace a plurality of the formations; then establishing a circulation of fluid between said sones externally of the casing; then introducing into the bore externally of the casing through one'of the zones a quantity of cement calculated to return in part through another; removing the excess cement within the casing; and' then perforating the casing and cement opposite at least one of the producing formations.

2. A method of preparing wells for production wherein a casing has been run in -a well bore characterised by; perforating the casing to establish at least two zones of communication from the interior of the casing to the space between the casing and the well bore; then introducing into the well bore externally of the casing through one of the zones a quantity of cement and venting the i'iuid displaced by the cement into the casing through another of the zones; and the perforating the casing and cement.

3. A method oi' preparing wells for production characterized by; drilling a well bore past a plurality of formations, including non-productive formations and those productive of water, gas, or oil,vas the case may be; running a casing in said bore; then providing at least two zones of ,com-1 munication between the casing and the well bore so positioned to embrace a plurality of the formations; then introducing into the bore externally of the casing through one of the zones a quantity of cement and venting the fluid displaced by the cement into the casing; and then perforating the casing and cement opposite at least one of the producing formations.

4. A method of preparing wells for production characterized by; drilling a well bore past a plurality of formations, including non-productive formations and those productive of water, gas, or oiLasthecasemaybe; runningacasingin said bore; then ming projectiles through the casing so as to establish. at least two sones of commimication between -the casing and well bore q'so positioned as to embrace a plurality of formations therebetween; then establishing a circulation of nuid between said sones externally of the casing; then introducing into the bore externally of the casing through one of the zones a quantity of cement calculated to return in part through another; and then firing projectiles through the casing and cement into at least one of the producing formations.

5. A method of preparing welk for production uponrunninga casinginawell-bore past a piurality of' formations, including those producing water, gas, or oil. as the case may be, said method characterized by; perforating the casing so as to establish at least two zones communicating with the exterior of the casing sindembracing a producing zone; sealing the interior of the casing between the zones; then introducing water through one of the sones into the well bore in ,osasos such a manner as to cause return now of the water into the casing through another of the zones, and continuing suchisupply of water until the well bore between that zones has been thoroughly washed; `and then forcing cement through one of the zones into the portion of the well bore cleaned by the water, in a suilicient quantity calculated to fill the same.

6. A method of preparing wells for production uponrunningacasingin awellborepastaplurality of formations, including those producing water, gas, or oil, as the case may be; firing projectiles through the casing so as to kestablish at leasttwo zones communicating with the exterior of the casing and embracing therebetween a producing zone; introducing a single tubing string into the casing; sealing the interior of the casing between the zones and around the tubing string; then introducing water through said tubing string'and out of one of the zones into the well bore in such a manner as to cause return flow of the water into the casing through another of the zones, and continuing such supply of water until the well -bore betwee'n the zones has been thoroughly washed; and then forcing cement through one of the zones into the portion of the well bore cleaned by the water, in a quantity calculated to nll the same; and then firing projectiles through the casing and cement and into a producing formation.

7. A method of preparing wells for production, characterized by: running a casing into a well bore; arranging atleast two zones of communication from the interior of the casing tothe space between the casing and well bore; introducing a tubing string into the casing; forming a sealing connection between the tubing string and casing and between said zones; establishing circulation of a washing fluid through the tubing string, externally of the casing between the zones, and between the tubing string and casing above the zones; then introducing a quantity of cement calculated to fill the space between the zones externally of the casing.

8.. A method of preparing wells for production, characterized by: running 4a. blank casing into a well bore past at least one producing formation; arranging at least two zones of communication from the interior of the casing to thespace between the casing and well bore; introducing a tubing string into the casing; forming a sealing connection between the tubing string and casing and between said zones; establishing circulation of a washing nuid through the tubing string, externally of the casing between the zones, and between the tubing string and casing above the zones; then introducing a quantity of cement calculated to fill the spme between the zones externally of the casing, and then perforating the casing and surrounding cement opposite a producing formation.

9. A method of preparing wells for production,

characterized by: running a blank casing into a well bore; perforating the casing to form two zones of communication with the surrounding bore; arranging at least two zones of communication from the interior of the casing to the space between the casing and well bore; intro# ducing a tubing string into the casing; forming a sealing connection between the tubing string and casing and between said zones; establishing circulation of a washing fluid through the tubing string, externally of the casing between the zones, and between the tubing string and casing above the zones; removing the tubing string; again perforating the casing to form e. second set oi two zones of communication withthe well bore, the lowermost of said zones being opposite and adjacent the calculated upper level of the previously introduced cement; then repeating the process of washing and cementing between the second set of zones.

' 10. A method of preparing wells for production characterized by; drilling a well bore past a plurality of formations, including non-productive formations and those productive of water, gas, or' oil, as the case may be; running a casing in said bore; providing a pair of zones communicating with the exterior of the casing; establishing circulation of fluid externally of the casing between said zones only; introducing into the bore externally of the casing through one of said pair of zones a quantity of cement calculated to illl the bore to the other of said pair of zones; providing successively other pairs of communicating zones and repeating the introduction of cement between said other zones.

11. A method of cleaning a well bore of drilling mud and deleterious matter for the purpose of facilitating the cementing of a casing within the well bore, wherein the well bore has been drilled past a plurality of formations including non-producing formations as well as those productive of water, gas or oil as the case may be and wherein blank casing has 'been landed, characterized fby: perforating said casing in at least two zones located opposite non-productive formations and embracing a productive formation, the relative spacing of said zones being suiliciently adjacent to insure flow of washing fluid externally of the casing therebetween; establishing two flow channels within said casing and communicating with said zones; and introducing a washing fiuid through one ow channel outwardly through one of said zones along the exterior of the casing between the zones and returning the washing fluid and, accumulated mud and deleterious matter through the other zone and flow channel.

, ly adjacent to insure flow of washing fluid externally of the' casing therebetween; introducing a tubing string into the casing to a point below the upper perforated zone; packing the space betweenthe tubing string and casing and intermediate said perforated zone, whereby the interior of said tubing string communicates with the lower perforated zone and the upper perforated zone communicates with the area between the tubing string above the packer and the surrounding casing; then introducing washing duid into one of said zones to cause its flow along the exterior 'of the casing to the other of said zones and return therethrough along with accumulated mud and deleterious matter.

13. A method of sectionally cleaning al well bore of drilling mud andfother'deleterious matter for the purpose of facilitating the cementing of the casing within the well bore, characterized by: perforating said casing in situ in at least two zones, the relative spacing of said zones being sumciently adjacent to insure now of washing uid externally of the casing therebetween; establishing two flow channels within said casing and commenting with said zones; and introducing a washing fluid through one flow channel outwardly through one of said zones along the exterior of the casing between the zones and returning the washing fluid and accumulated mud and deleterious matter through the other zone and flow channel.

14. A method o1' sectionally cleaning a well bore of drilling mud and other deleterious matter for the purpose of facilitating the cementing oi the casing within the well bore, characterized by: perforating said casing in situ in at least two zones, the relative spacing of said zones being sutilclently adjacent to insure ilow of washing 'iluid rated zone communicates with the area. betweenV the tubing string above the packer and the surrounding casing; then introducing washing fluid into one of said zones to cause its flow along the exterior oi the casing to the other of said zones and return therethrough along with accumulated mud and deleterious matter.

WALTER T. WELLS. 

